To stimulate health system transformation, the Centers for Medicare and Medicaid Services (CMS) launched the State Innovation Model (SIM) Initiative, which since 2013, has invested more than 1 billion dollars in state efforts to plan, piot test, and implement payment and delivery system reforms. The SIM Initiative is an ongoing, naturally occurring federal-state policy intervention that provides financial and technical support to states for development and testing state-led multi-payer health care payment and service delivery models. The goals of this federal-state program are to improve health system performance, improve the quality of patient care, and decrease health care costs for all residents of the state. As states are investing in transformational restructuring of incentives and delivery systems, the SIM Initiative is anticipated to improve health status overall, including diabetes risk and health status in large segments of the community. In order to achieve SIM Initiative goals, most SIM states are focusing on chronic illness, in general, and diabetes, in particular. We propose a natural experiment rigorously designed to optimize the ability to draw causal inferences. Using diverse data from multiple sources we will assess this population-targeted policy to assess outcomes at multiple levels, including state, county, and physician organization and delivery system levels. From 2015 to 2019, we will monitor and track payment and delivery system reforms relevant to preventing, and managing complications of, diabetes. This will be done for 18 purposively sampled states: 6 Round 1 states, 6 Round 2 states, and 6 waiting control states. Using these policy data, we will develop a taxonomy of state SIM implementation to empirically examine how SIM implementation affects practice implementation of the patient-centered medical home (PCMH) model and participation in accountable care organizations (ACOs). We will use propensity score matching of patients in a stepped wedge research design to examine the impact of the staged implementation of SIM plans across the states. We will estimate the impact of the SIM Initiative on diabetes-related health behaviors (2011-2018) and hospitalizations due to diabetes (2011-2017) for Round 1 vs. Round 2 vs. waiting control states. The influence of delivery system and payment reform activities implemented as part of each states' SIM plan will be explored. Finally, we estimate the economic impact of the SIM Initiative's improvements in diabetes care prevention and management and explore heterogeneity in economic impacts across SIM states. The proposed collaborative project will yield actionable data and analyses to state and local health officials, and public health and health care delivery stakeholders on the impact of the SIM Initiative on improvements on diabetes prevention and management.